Thresholds can be defined per interface, per switch, or globally. If a threshold is defined for a switch, then that threshold setting is used for each of the interfaces on the switch, unless specific thresholds for interfaces themselves are defined. Similarly, the global threshold setting is used for all switches and interfaces, unless overridden at the switch or interface level.
A threshold is configured using the edit threshold dialog. This can opened in a number of ways:
Finally, when viewing a table of interfaces (ie by selecting All interfaces, or a single switch), a specific interface's thresholds can be configured by clicking the edit button to the left of the interface number or name.
A useful way to see which thresholds have been customised is to select Customised thresholds to view. This will show all the switch and interface thresholds which have been customised; allowing their status to be observed, and their configuration changed.
When you open the edit threshold dialog, you can then enter the settings desired for each threshold parameter.
See Section 7.2, “Threshold values and types” for a description of the settings for each threshold. By default, a switch threshold will be set to the global threshold setting, and an interface threshold will be set to the threshold setting for its switch. To customise the threshold, first uncheck the Use global thresholds (for a switch) or Use switch thresholds checkbox (for an interface), to allow the settings to be changed. If you want to remove the custom settings, and revert to the default, just re-check the checkbox.